I asked this question to Thor Customer Service about my 2015 Vegas 24.1. There is NO wire harness and plug tucked away under the dash for a brake controller.
They told me the 7-way plug next to the receiver on the rear is wired for tail lights and brakes. I don't know if the 12 VDC to pin 4 is wired. They told me the blue wire for the brake controller is wired to the 7-way and is capped off near the fuel tank.
I'd have to wire the power, ground, and blue wire under the dash and run the blue wire up to the connector for the brake controller.
I recommend you verify with Thor whether there is a brake controller connector wired and tucked under your dash for your specific VIN. I'd also go to my dealer and have them hook up a trailer simulator to verify what is wired and working on your 7-way. I know of two owners on this forum that wired their brake controller and had to redo the factory's wiring job on the 7-way because Thor did it wrong.
Ed & Bev Felker
Retired USAF Col and retired Nurse
Traveling with Lily & Bella ('Teddy Bear' breed)
2015 Vegas 24.1 (E-350)